Synthesis, characterization and antimicrobial activity of macrocylic phenoxo-bridged di- and tetra-nuclear complexes from N,N-bis[2,6-diiminomethyl-4-methyl-1-hydroxyphenyl]succinoyl/sebacoyldicarboxamides

Macrocyclic ligands N,N-bis[2,6-diiminomethyl-4-methyl-1-hydroxyphenyl] succinoyl dicarboxamide (H2L1) and N, N- bis[2,6-diiminomethyl-4-methyl-1-hydroxyphenyl] sebacoyl dicarboxamide (H2L2) were synthesized and characterized by various spectral techniques. Macrocyclic di- and tetra-homonuclear phenoxo bridged Cu-II, Co-II, Ni-II, Zn-II, Cd-II and Hg-II complexes have been synthesized through the template method by using the precursors 2,6-diformyl- 4-methylphenol, succinoyldihydrazide/sebacoyldihydrazide and respective metal chlorides in 2: 2: 2/2: 2: 4 ratio respectively. The synthesized complexes were characterized by i.r., n.m.r., u.v.-vis., FAB-mass, e.s.r., magnetic susceptibility and elemental analyses data. The elemental analyses and FAB-mass spectral data have justified the dinuclear and tetra nuclear structure for the complexes of the ligands H2L1 and H2L2 respectively. The observed low magnetic moment values revealed the existence of antiferromagnetic spin exchange interaction operating between the two metal centers. Electronic data suggested the octahedral geometry for Ni-II complexes and square pyramidal geometry for Cu-II, Co-II, Zn-II, Cd-II and Hg-II complexes of both the ligands. The Cu-II, Co-II and Zn-II complexes of both the ligands have shown good antifungal activity against Aspergillus niger and Fusarium oxysporum and medium to weak antibacterial activity against Escherichia coli and Staphylococcus aureus when compared to the standard drugs Grisefulvin and Ciprofloxacin respectively.